DS got his first tooth when he was about 9 or 10 months. When he was 1, he still only had the bottom two...
I'm reasonably sure that our dentist told me that tooth loss correlates with when the first ones came in. This statement describes my kids perfectly: DS9 got and loses teeth exactly on schedule. DS7.5 got his first tooth at 10 months and still only has two permanent teeth on the bottom (the dentist said that "his mouth looks 6 years old" but he wasn't concerned).
Meanwhile, DD4 got her first teeth when she was 4 or 5 months old and she's already lost the first one with another one loose. I'm actually concerned that her mouth is too small to accommodate too many new teeth.
Val